Actually, they are not.Clemson is an AAU member.
AAU Members Here
It appears of the ACC, only Duke, Georgia Tech, North Carolina, and Virginia are among the esteemed AAU colleges. And here I thought most of them were.
Nine of the twelve Pac 12 schools are.
Of the former Big 12, Iowa State, Kansas, Missouri, Texas, and Texas A&M are.
All of the Big Ten are except Nebraska, who was when they joined.
Notre Dame, despite a lot of self-righteous haughtiness, is not.